I can confirm that unity greeter fails if no user account is shown.
As a workaround you can set the following in /etc/lightdm/lightdm.conf:
[SeatDefaults] greeter-hide-users=true
as this shows a username entry instead of a user list (which is probably what you want anyway).
I can confirm that unity greeter fails if no user account is shown.
As a workaround you can set the following in /etc/lightdm/ lightdm. conf:
[SeatDefaults] hide-users= true
greeter-
as this shows a username entry instead of a user list (which is probably what you want anyway).